1. Field of the Invention:
The present invention relates to slide fasteners, and more particularly to a slide fastener assembly for closure of a case or folder having a pair of outer walls and at least one intermediate wall or partition.
2. Description of the Prior Art:
As disclosed in U.S. Pat. No. 2,483,057 and Japanese Patent Publication (Kokoku) No. 56-27243, a known slide fastener for a case or folder comprises a pair of spaced outer stringers adapted to be attached to a pair of outer walls, respectively, of the case, and an intermediate stringer adapted to be attached to an intermediate wall or partition of the case. The outer stringers have on their inner longitudinal edges a pair of rows of ordinary or single-headed coupling elements, and the intermediate stringer has on one longitudinal edge a row of special or double-headed coupling elements that is interengageable on opposite sides with the respective rows of ordinary coupling elements of the outer stringers in such a manner that the outer and intermediate stringers are disposed in generally T-shaped configuration as viewed in transverse cross section. Following are common problems with the prior slide fastener:
(1) Because of their special structure, double-headed coupling elements cannot be manufactured at low cost, thus making the slide fastener expensive.
(2) In attachment of the slide fastener to the case, the intermediate stringer's tape is sewn or bonded to the intermediate wall of the case, while the intermediate stringer tape is simply put over a peripheral portion of the intermediate case wall only at one face thereof, which causes unstable positioning and thus inaccurate attachment of the intermediate stringer.
(3) Since the intermediate stringer is secured to the intermediate case wall with the peripheral portion of the latter being left floating, the peripheral portion is not embraced by the stringer tape or any other part and hence tends to be caught by a slider.
FIG. 1 of the accompanying drawings illustrates another prior slide fastener in which an intermediate stringer 1 comprises a tape of T-shaped cross section including a pair of horizontal tape sections 2, 3 carrying on their outer longitudinal edges a pair of rows of ordinary coupling elements, and a vertical tape section 4 projecting downwardly from the joint of the two horizontal tape sections 2, 3. The intermediate stringer 1 is interengageable on opposite sides with a pair of outer stringers 5, 6 by means of a pair of sliders 7, 8, respectively, the respective tapes of the outer stringers 5, 6 being sewn to a pair of outer walls 9, 10 of a case. In this prior art, like the prior art of U.S. Pat. No. 2,483,057 and Japanese Patent Publication No. 56-27243, the vertical tape section 4 of the intermediate stringer 1 is sewn to an intermediate case wall 11 with the peripheral portion 11a of the later being left floating; therefore this peripheral portion 11a tends to be caught by the slider 7.